feat: enable bf16 fallback for o_proj in Qwen3-VL W8A8 quantization

[nie-linfeng]

Problem

When o_proj weights fall back to bf16 in a W8A8 quantized model, the ATB LinearOperation fails with a dtype mismatch error:
CheckIniMatch Failed! Supported Combs:
[comb0]: inTensor0(int8,nd), inTensor1(int8,nd), inTensor2(int32,nd), inTensor3(float,nd), outTensor0(bf16,nd)

Solution

Reuse the non-quantized adaptation pattern for o_proj:

[gemini-code-assist]

Code Review

This pull request introduces support for non-quantized (bf16) o_proj in the Qwen3 decoder loader and layer implementation. It detects whether o_proj is quantized by checking the size of the attention output bias tensor, and dynamically updates the linear layer descriptors to BFLOAT16 if it is not. Feedback was provided regarding a style guide violation where the constant DENSE_LINEAR_INDEX should be renamed to kDenseLinearIndex to adhere to the k + PascalCase naming convention.

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[gemini-code-assist]

According to the repository style guide, constants should be named using k + PascalCase (e.g., kDenseLinearIndex instead of DENSE_LINEAR_INDEX). Please update the constant name to adhere to the style guide.

Suggested change

	constexpr uint64_t DENSE_LINEAR_INDEX = 3;
	auto update_o_proj = [](atb_speed::qwen::QwenLayerParam& p) {
	p.linearDescs[DENSE_LINEAR_INDEX] =
	static_cast<int>(LinearTypeV2::BFLOAT16);
	p.linearQuantType[DENSE_LINEAR_INDEX] =
	static_cast<int>(LinearType::INVALID);
	};
	constexpr uint64_t kDenseLinearIndex = 3;
	auto update_o_proj = [](atb_speed::qwen::QwenLayerParam& p) {
	p.linearDescs[kDenseLinearIndex] =
	static_cast<int>(LinearTypeV2::BFLOAT16);
	p.linearQuantType[kDenseLinearIndex] =
	static_cast<int>(LinearType::INVALID);
	};

References

1. Constants must be named using 'k' + PascalCase (e.g., kContentLength, kMaxBatchSize). ^(link)